Question

a car of 1500 kg travelling at the speed of 63 km/h comes to halt after 10s .calculate the force applied to stop the car
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Answer 1

Explanation:

Mass of the car m = 1500 kg

Velocity of the car v = 60 km/h

= 60×1000 /60×60 = 50 /3 m/s

The car is in motion, so its energy = kinetic energy = 1 /2 mv2

= 1 /2 (1500) ( 50/ 3 ) 2 J

= 1/ 2 × (1500) × 2500/ 9 J

= 208333.3 J

The kinetic energy of the car, when it comes to rest = 0 J

Work done on object = change in kinetic energy

= 208333.3 − 0 J

= 208333.3 J

Hence, the work required to stop the car is 208333.3 J

Answer 2

Answer:

F = 2625 N

Explanation:

F = ma

m = 1500 Kg

F ( force applied )

m = mass of the car

a = acceleration the car is moving

$a = \frac{v-u}{t}$

u ( initial velocity ) = 63 $\frac{km}{h}$ ( given in question )

v ( final velocity ) = 0 ( as it comes to rest )

t = time taken to come to 0 km/h from 63 km/h = 10 s =

u = 63 × 5/ 18 =  17.5 m/s

So now we must calculate the acceleration of the car .

$a = \frac{v-u}{t}$

a = (0 - 17.5 ) / 10

a = -1.75

find the magnitude of the acceleration

a = │ - 1.75 │

a = 1.75 m/s²

F = ma

F = 1500 ×  1.75  

F = 2625 N